Thousands of Brits embark on cruise holidays each year, and the Cruise Lines International Association said ships work closely with international authorities to ensure passenger safety.

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CRUISE: Ships in the Med could be in danger

Vice-Admiral Clive Johnstone told the Telegraph: "We know they have had ambitions to go off shore, we know they would like to have a maritime arm, just as al Qaida had a maritime arm.”

Tourist or commercial ships are still increasingly at risk, the officer warned.

He added: “There is a horrible opportunity in the future that a misdirected, untargeted round of a very high quality weapons system will just happen to target a cruise liner, or an oil platform, or a container ship.”

Vice-Adml Johnstone said: “I think it won’t be a planned, horrible mischievous act, I think it will be an act which is almost a mistake, or it will be an act of random terrorism that will suddenly have extraordinary implications for the Western world.”

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“It will be an act of random terrorism that will suddenly have extraordinary implications for the Western world”

Vice-Admiral Clive Johnstone

A spokesman for the Cruise Lines International Association said: "As always, cruise liners coordinate closely with national and international security and law enforcement authorities around the globe to help ensure passenger safety.

"Security staff are well-trained and experienced; some are former law enforcement officers. Port and onshore facilities, infrastructure, and passenger security and services in destinations are strictly scrutinized.

"In the event of any safety concerns, cruise ships have the flexibility to alter their itineraries as needed to avoid areas of higher risk. Our priority is to provide for the safety of passengers and crew at all times."